1. Technical Field
The present disclosure relates to a head-mounted display device.
2. Description of the Related Art
Among head-mounted display devices, there are devices of so-called see-through type that have a function which allows an observer to simultaneously observe a scene on outside of the display device and an image displayed in the display device without interruption of view of the observer. Hereinbelow, the function will be referred to as “see-through function” and will be described.
This technique is intended for making it easier for the observer viewing an image displayed in the head-mounted display device to take another action, avoiding a risk that may be caused by the interruption of the view when the device is used outdoors, or the like.
Methods for attaining the see-through function fall roughly into following two categories.
In one category, as disclosed in Japanese Unexamined Patent Application Publication No. 4-208996, an optical component placed in front of an eye of an observer, among components that form the display device, is provided as a half mirror.
In this method, light on the outside of the display device penetrates through the half mirror and is incident on the eye of the observer. Thus the method attains the see-through function that allows superposition and simultaneously view of the scene on the outside of the display device and the displayed image.
In the other category of methods, as disclosed in Japanese Unexamined Patent Application Publication No. 2006-3879, a component placed in front of an eye of an observer, among components that form the display device, has a decreased size.
In the method disclosed in Japanese Unexamined Patent Application Publication No. 2006-3879, the see-through function is attained by making the optical component placed in front of the eye of the observer, among the components that form the display device, thinner than a diameter of a pupil of the observer so that an image displayed in the display device and light on the outside of the display device may respectively be projected on partitions of the pupil.